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Biomedical subjects

S H Koh

Publications and source records attributed to S H Koh.

24 records · Page 2Linked to original sources
PubMed1981

The effect of calfhood vaccination with strain 19 on the serological diagnosis and eradication of bovine brucellosis.

Data from 42,224 cattle from 694 herds collected during the brucellosis eradication campaign were used to examine the effects of calfhood strain 19 vaccination. The prevalence to infection in vaccinated herds was 1.8% compared with 9.1% in non-vaccinated herds (p less than 0.005). The mean titre in the former group was lower (p less than 0.001). Vaccinated herds required 3.3 herd tests to achieve a provisionally free status compared with 4.8 in non-vaccinated herds (0.001 less than p less than 0.005). Vaccination did not significantly reduce the number of herd test in herds with less than 100 breeding females. In tests after the initial herd test only 0.5% reactors were found in vaccinated herds compared with 6.9% in non-vaccinated herds (p less than 0.005). There were 0.9% false positive to the Rose Bengal plate test in non-vaccinated and 2.1% in vaccinated animals (p less than 0.005) in non-infected herds. In infected herds this percentage was 3.0% and 4.2% respectively by (p less than 0.05). In the non-infected herds there were 0.04% false positives to the complement fixation tests out of 10,506 non-vaccinated cattle tested and 0.2% out of 24,734 vaccinated cattle.

Animals↗
PubMed1978

Control of concanavalin A receptor mobility by cytoplasmic actin in human tumour cells.

Tissue culture monolayers of seven human intracranial tumours comprising 2 astrocytomas, 3 meningiomas, 1 secondary squamous cell carcinoma and 1 secondary adenocarcinoma were examined by a double immunofluorescent staining technique to demonstrate Concanavalin A (Con A) surface receptors and cytoplasmic actin in the same cell. Tumour cells, treated with fluoresceinisothiocyanate-labelled Con A (FITC-Con A) showed staining in cell margins or in a random distribution over the cell surface. Incubating the cells with FITC-Con A at 37 degrees for increasing periods of time resulted first in staining of clusters and later of perinuclear globules. Cells, pretreated with 4% paraformaldehyde at 4 degrees for 10 min or with cytochalasin B at 37 degrees for 30 min showed staining restricted to cell margins. In the cytochalasin B-treated cells, the peripheral staining was in the form of coarse clusters. Double fluorochrome studies showed that the anti-actin antibody (AAA) staining occurred in sites closely related to those stained by FITC-Con A both in untreated as well as in cytochalasin B-treated cells. The findings suggest that Con A receptors, as an example of a stable cell membrane determinant in human tumour cells, are associated with actin and that their mobility on the cell surface is dependent on an intact cytoplasmic actin system.

Actins↗
PubMedDate not supplied

A high-resolution add-on in-lens attachment for scanning electron microscopes.

A compact add-on objective lens for the scanning electron microscope (SEM) has been designed and tested. The lens is < 35 mm high and can be fitted on to the specimen stage as an easy-to-use attachment. Initial results show that it typically improves the spatial resolution of the SEM by a factor of three. The add-on unit is based upon a permanent magnet immersion lens design. Apart from the extra attachment to the specimen stage, the SEM with the add-on lens functions in the normal way. The in-lens unit can comfortably accommodate specimen heights up to 10 mm. The new add-on lens unit opens up the possibility of operating existing SEMs in the high-resolution in-lens mode. By using a deflector at the top of the add-on lens unit, it can also operate as a quantitative multichannel voltage contrast spectrometer, capable of recording the energy spectrum of the emitted secondary electrons. Initial experiments confirm that a significant amount of voltage contrast can be obtained.

Journal Article↗
PubMedDate not supplied

Effects of topical fluoride treatment on tensile bond strength of pit and fissure sealants.

Clinicians often do not place pit and fissure sealants immediately after topical fluoride treatment because fluoride treatment might reduce bonding to enamel. The effect of NaF, SnF2, and APF on the in-vitro bond strength of two sealants to enamel was determined. The fluoride treatments and control (artificial saliva) were applied to enamel surfaces for four minutes and rinsed. A filled sealant (FluoroShield) and an unfilled sealant (Concise) were bonded to the etched enamel and debonded in tension using a universal testing machine. NaF increased the bond strength of the unfilled sealant; SnF2 and APF had no significant effect. NaF and APF decreased the bond strength of filled sealant while SnF2 had no significant effect. The bond strength of the filled sealant was higher than or equal to that of the unfilled sealant. Exposure of enamel to NaF, SnF2, or APF prior to placement of unfilled or filled sealants has no effect on in vitro bond strength between the enamel and the sealants.

Acidulated Phosphate Fluoride↗